1. Field of the Invention
The present invention relates to providing lubrication to a variable valve system for an internal combustion engine.
2. Description of the Related Art
A valve operating mechanism known in the art includes a pair of intake valves, a drive shaft extending in the front-to-rear direction of an engine, a camshaft provided for each cylinder and rotatably and coaxially supported on an outer peripheral surface of the drive shaft, a drive cam provided at a predetermined position along the drive shaft, a pair of oscillating cams for opening the intake valves, a transmission mechanism connected between the drive cam and one of the oscillating cams so as to transmit rotation force of the drive cam as oscillating force (valve opening force) of the oscillating cam, and a control mechanism for changing the operating position of the transmission mechanism.
The transmission mechanism includes a rocker arm provided above the drive shaft, a link arm linking one end of the rocker arm and the drive cam, and a link rod linking the other end of the rocker arm and a cam-nose portion of one of the oscillating cams. The control mechanism includes a control shaft rotatably supported by a bearing provided above the drive shaft, and a control cam fixed to the outer periphery of the control shaft and serving as a fulcrum of the oscillating motion of the rocker arm.
The rocker arm has a support hole that rotatably supports the control cam. The link arm has a fitting hole rotatably connected to an outer peripheral surface of the drive cam, and a pin hole to which a pin projecting from the rocker arm is connected.
Lubricant is supplied from a lubricant flow path provided in the drive shaft into the space between the outer peripheral surface of the drive cam and an inner surface of the fitting hole of the link arm, and into the space between the pin of the rocker arm and the pin hole of the link arm. Lubricant is also supplied from a lubricant flow path, which extends in the axial direction in the control shaft, into the space between the support hole of the rocker arm and the control cam.